1. Field of Invention
Trolley poles for electric vehicles, especially industrial vehicles, such as mine mules, that work in confined areas, must be rotatably mounted so that the trolley carried thereon may be pulled, rather than pushed, along the overhead trolley wire, irrespective of the direction the vehicle of application might be traveling at any given time. This necessitates that the trolley pole be turned 180.degree. every time the direction of travel is reversed, which is usually the responsibility of the motorman or operator of the vehicle. If the pole is constrained against accidental turning merely by reliance upon the trolley's tracking the trolley wire, a hazardous situation for the operator arises every time the trolley jumps off the trolley wire, when the heavy trolley pole is freed to thrash about, sometimes hitting the operator in the head. Even if the trolley stays in place, the operator, upon manually turning the trolley pole for reversing the direction of travel, must lean over into the confined space between the locomotive and the overhead to effect the transfer, thus to incur the risk of accidentally contracting the trolley wire that could prove fatal.
2. Description of the Prior Art
Devices for restraining the accidental turning of trolley poles, as in conventional street railway trolley cars, have been known since the last century; e.g., the U.S. Pat. Nos. to Thomson, 440,665 and Brown, 582,259, both of which show turntable mounts for trolley assemblies, and latch mechanisms for locking them against turning from a selected latched position. In such cases, unlimited space and ease of accessibility allow for unlatching the pole and turning it to the second selected position without hazard to the operator, who may accomplish the entire operation from inside the car (Thomson, FIG. 1), or remotely by ropes on lines from alongside the car, as suggested by Brown.
More closely identified with the problem, however, are the U.S. Pat. Nos. to Shanaberger, 1,437,780 and Packer, 1,848,140, both of which deal with trolley mounts and controls for electric mine mules or locomotives. Still another adaptation employs an air-cylinder to actuate a cam retainer in response to a foot-treadle valve on the floor of the operator's cab. These devices are too elaborate and complicated given the rugged environment in which they are expected to operate, and are subject to accidental misuse with consequent peril to the operator.